Radiators for motor vehicles serve for cooling an internal combustion engine and are connected to a coolant circuit which consists essentially of a radiator forward flow or engine return flow, of a radiator return flow or engine forward flow with coolant pump and of a bypass with a thermostatic valve. A multiplicity of secondary circuits, for example for a charge air cooler or an oil cooler, are connected to such a coolant circuit, the individual circuits having a different temperature level and therefore being separated from one another by means of separate chambers. The chambers are part of header boxes of the coolers and are divided off from one another by means of partitions. During the filling or emptying of the radiator of the coolant circuit, the individual chambers are to communicate with one another, so that a more rapid and a uniform filling without air inclusions and, likewise, a faster emptying are possible.
It was therefore proposed, in DE-A 100 41 122, to connect the individual chambers of a header box to one another by means of a duct, each chamber being fluidically connected to the duct interior via a connecting orifice. The duct of hollow-cylindrical design can have inserted in it a tubular connection piece with connecting orifices which are arranged in the same positions as the orifices in the connecting duct. By the tubular connection piece being rotated about its longitudinal axis, these orifices can, on the one hand, be brought into congruence, so that all the chambers communicate with one another, and, on the other hand, are closed by further rotation. This solution has the disadvantage that, in the closed state, the sealing off of the individual chambers with respect to one another is inadequate, because this sealing takes place only via the gap between the tubular connection piece and the duct inner wall. The selected gap must therefore be relatively small, thus resulting, in turn, in relatively high adjustment forces for adjusting this actuating member. Moreover, under certain circumstances, the use of special sealing elements of complicated configuration is required in order to obtain permanent and complete leaktightness.